Lifetime, critical nucleus size, and laplace pressure of individual electrochemically generated nanobubbles

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Title Lifetime, critical nucleus size, and laplace pressure of individual electrochemically generated nanobubbles
Publication Type dissertation
School or College College of Science
Department Chemistry
Author German, Sean R.
Date 2017
Description This dissertation presents experimental and computational studies of individual nanobubbles electrochemically generated at platinum nanoelectrodes. Chapter 1 provides an overview of the physics governing bubble dynamics and a brief summary of the literature regarding nanobubbles. Chapter 2 describes a fast scan voltammetric method for measurement of nanobubble dissolution rates. After a nanobubble is nucleated from gas generated via an electrode reaction, the electrode potential is rapidly stepped to a value where the bubble is unstable and begins to dissolve. The electrode potential is immediately scanned back to values where the bubble was initially stable. Depending on the rate of this second voltammetric scan, the initial bubble may or may not have time to dissolve. The fastest scan rate at which the bubble dissolves is used to determine the bubble’s lifetime. The results indicate that dissolution of a H2 or N2 nanobubble is, in part, limited by the transfer of molecules across the gas/water interface. Chapter 3 presents electrochemical measurements of the dissolved gas concentration, at the instant prior to nucleation of a nanobubble of H2, N2, or O2 at a Pt nanodisk electrode. The results are analyzed using classical thermodynamic relationships to provide an estimate of the size of the critical gas nucleus that grows into a stable bubble. This critical nucleus size is independent of the radius of the Pt nanodisk employed and weakly dependent on the nature of the gas. Chapter 4 reports electrochemical measurements of Laplace pressures within single H2 bubbles between 7 and 200 nm radius (corresponding, respectively, to between 200 and 7 atmospheres). The current, associated with H2 gas generation, supporting a steady-state nanobubble is modulated by application of external pressure. The slope of the current-pressure response allows extrapolation of the bubble’s curvature-dependent internal pressure. The results demonstrate a linear relationship between a bubble’s Laplace pressure and its reciprocal radius, verifying the classical thermodynamic description of H2 nanobubbles as small as ~10 nm. Chapter 5 summarizes these results and places them in the context of current research. Future directions for further studies are suggested.
Type Text
Publisher University of Utah
Subject Pure sciences; Applied sciences; Bubble dynamics; Nanobubble; Platinum nanoelectrodes
Dissertation Name Doctor of Philosophy
Language eng
Rights Management ©Sean R. German
Format application/pdf
Format Medium application/pdf
ARK ark:/87278/s6906854
Setname ir_etd
ID 1347749
Reference URL https://collections.lib.utah.edu/ark:/87278/s6906854
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